// Assume minuend >= subtrahend >= 0
void Sub(int minu[], int subt[], int diff[], int max_digits) {
   int update[max_digits];
   update = minu;  // Array assignment
   for (int digit = 0; digit < max_digits; digit++) {
      if (update[digit] < subt[digit]) {
         update[digit] += 10;
         int i = digit + 1;
         while (update[i] == 0) {
            update[i] = 9;
            i++; 
         }
         update[i]--;
      }
      diff[digit] = update[digit] - subt[digit];
   }
}
